Lines of Credit (Details) (USD $)	12 Months Ended
Dec. 31, 2010	Dec. 31, 2009
Lines Of Credit (Textuals) [Abstract]
$ 1.425 billion unsecured revolving credit facility	$ 1,425,000,000
Line of credit commitment by bankrupt financial institution now unavailable	75,000,000	75,000,000
Line of Credit Maturity	Feb. 28, 2012
500.0 million ability to increase	500,000,000
Advances under credit facility, rate plus spread	0.0050
Face value of convertible unsecured debt	1,280,000,000	1,370,000,000
Amount restricted/dedicated to support letters of credit	147,300,000	56,700,000
Line of credit amount outstanding	$ 0	$ 0
Weighted average interest rate on revolving letter of credit	0.66%

Represents the amount by which available borrowings on the unsecured revolving credit facility may be increased. The available borrowings may be increased by adding additional banks to the facility or obtaining the agreement of existing banks to increase their commitments.

Name:	eqr_AbilityToIncreaseLineOfCredit
Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents a spread that is dependent upon a credit rating or bids received from lenders and is blended with an interest rate for amounts borrowed under the credit facility.

+ Details

Name:	eqr_LineOfCreditFacilitySpread
Namespace Prefix:	eqr
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the line of credit is scheduled to be fully repaid, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

+ Details

Name:	eqr_LineOfCreditMaturity
Namespace Prefix:	eqr
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Lines Of Credit.

+ Details

Name:	eqr_LinesOfCreditTextualsAbstract
Namespace Prefix:	eqr
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents a reduction in borrowing capacity under the unsecured revolving credit facility due to a credit provider's declaration of bankruptcy.

+ Details

Name:	eqr_ReductionOfBorrowingCapacity
Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The weighted average interest rate on the revolving line of credit during the period.

+ Details

Name:	eqr_WeightedAverageInterestRateRevolvingCreditFacility
Namespace Prefix:	eqr
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount borrowed under the credit facility as of the balance-sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityAmountOutstanding
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Net increase or decrease in the carrying amount of the credit facility for the period for reasons other than accrued, but unpaid interest, additional borrowings, repayments, and forgiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph f
-Article 4

+ Details

Name:	us-gaap_LineOfCreditFacilityIncreaseDecreaseOtherNet
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 2, 4

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant